Field of the Invention
The present invention relates to a dust cover for a ball joint.
Further, the present invention relates to a dust cover for a ball joint which is used in an automobile suspension device, and a steering device.
Description of the Conventional Art
Conventionally, in a ball joint to which a dust cover is installed for the purpose of a dust prevention and a water prevention in a ball joint coupling portion, the ball joint has been classified into two kinds including a taper alignment ball joint as shown in FIG. 5, and a pinch bolt type ball joint as shown in FIGS. 6 and 7.
These two kinds of ball joints are different mainly in a fastening method between a knuckle and a stud.
In the taper alignment ball joint shown in FIG. 5, a position of a knuckle 500 is decided at a position where a taper surface of a shaft 400 of a ball stud 100 overlaps.
More specifically, since the taper alignment ball joint is structured such that no gap exists between a surface of the shaft 400 and the knuckle 500, water and dusts can be prevented from entering into a dust cover 600 by bringing a dust lip 710 provided in the other end small-diameter opening portion 700 of the dust cover 600 into contact with a lower surface of the knuckle 500 (a surface in the dust cover 600 side).
However, the pinch bolt type ball joint shown in FIGS. 6 and 7 is structured such that a knuckle 500 is provided with a notch portion 510 which reaches a surface of a shaft 400 from the knuckle outer peripheral surface, a gap of the notch portion 510 is narrowed by being fastened by a fastening means 520 such as a bolt, and the knuckle 500 is fixed to the shaft 400.
As a result, even if the dust lip 710 as shown in FIG. 5 is provided in the other end small-diameter opening portion 700 of a dust cover 600 shown in FIG. 7, the water and the dusts can not be prevented from entering into the dust cover 600.
Further, there has been made an attempt to arrange a washer-like seal member in a lower surface of the knuckle (a surface in the dust cover side), however, the water and the dusts could not be prevented from entering into the dust cover (Japanese Unexamined Utility Model Publication No. 58-130118).
Particularly, since the washer-like seal member rotates together with the knuckle according to an oscillating and rotating motion of the knuckle, a sealing performance is lowered.
As a countermeasure for preventing the corotation, there has been proposed a structure in which a convex portion corresponding to the notch portion of the knuckle is provided in a surface of the washer-like seal member, however, it has been impossible to completely prevent the corotation.